Barker's Method

This program finds values of the parameters in the 4-suffix Margules equations that provide the best fit to a set of vapor-liquid equilibrium data.   The 4-suffix Margules equations are:

ln g1 = x22{A12 + 2(A21 - A12)x1 + Cx1(3x1 - 2)} 

ln g2 = x12{A21 + 2(A12 - A21)x2 + Cx2(3x2 - 2)}  

where g1 and g2 are the liquid phase activity coefficients for species 1 and 2 and where A12, A21 and C are the parameters.

 

The program has the following characteristics:

  • Data are assumed to be in the form of pressure P vs. liquid phase mole fraction x1 for a binary system at constant temperature.
  • The vapor phase is assumed to be an ideal gas and Poynting corrections are assumed to be negligible.
  • The program determines the optimum 4-suffix parameters A12, A21 and C by minimizing the sum of the squares of the differences between the experimental and calculated pressures.  The flexible polyhedron search of Nelder and Mead is used.
  • Output consists of the optimum 4-suffix Margules parameters and resulting calculated pressures and vapor phase compositions y1 for each experimental x1 value.  Values of deviations between experimental and calculated pressures also are given.

    

  Click here to regress an example set of data (Acetone(1)+Toluene(2) at 30 oC).

 

  Click here to enter your own set of vapor liquid equilibrium data.

 
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